INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH K.Arulkumar et al., Vol.6, No.3, 2016 Recent Advances and Control Techniques in Grid Connected Pv System – A Review K.Arulkumar *‡ , K.Palanisamy ** , D.Vijayakumar *** *** School of Electrical Engineering, VIT University, Vellore. karuleee@gmail.com,vijayakumar.d@vit.ac.in,kpalanisamy@vit.ac.in *‡ Corresponding Author; K.Arulkumar, VIT University,Vellore,India,karuleee@gmail.com. Tel: +91 9994822651 Received: 12.04.2016 Accepted: 01.06.2016 Abstract- In recent years, grid connected photovoltaic system has emerged with its simplicity, reliability and endurability. The ranges of grid tie inverters (GTI) are classified as small scale as several tens of kilowatts and large scale as hundreds of megawatts. Accordingly, the standard of interconnecting to the grid is made higher extent in improving its power system reliability, efficiency and cost. Moreover, the working of grid connected inverter primarily depends on robustness in control strategy, even working in abnormal grid conditions such as deviation of voltage and frequency. This review focuses on updating grid standard codes and regulations, in addition overview of recent control strategies and direct power control. The structure of the phase locked loop (PLL) with grid synchronization techniques for single phase and three phase is discussed in brief. Investigations are performed for a fault ride through capabilities with detailed analysis of islanding detection methods with its types. The PV- STATCOM control functionality for the enhancement is discussed in detail. Keywords: PV inverter, grid codes, islanding, power quality, grid synchronization, current control 1. Introduction Solar photovoltaic (PV) energy conversion system has shown increase at a moderate annual rate of 60% in the last five years [1]. This is possible because of alternate clean energy sources, reduction of cost, efficiency increase of PV modules and subsidy scheme of political regulations [2]. PV installation is classified according to their functional and operating requirements named standalone and grid connected. With standalone system, remote area is supplied by DC or AC power with converters and energy storage devices [3]. On the other hand, in grid connected, generated power supply to the utility services without any energy storage equipments that have made added advantage of 99% benefit than stand alone system. In grid connected inverter, the power generated by PV plant is directly given to the transmission line and it is distributed. Henceforth, the use of batteries and other energy storage devices is not required that makes the arrangement less space, reduced investment cost and maintenance than stand alone system [4-6]. The evolution of solid state inverter technology and its control strategy have established PV systems into the grid as shown in Fig. 1. Due to variation of input supply at the inverter side, the PV inverter topology and its control design is made robust with the promising contol structure. The dc-link voltage is fixed to supply constant voltage to the inverter. In the present decades, transmission system operators (TSO) have come up with standard grid codes in improving the quality of power supply injected into the grid based on small, medium and large scale industries according to the generated power rating. National electricity regulatory authority has made it mandatory to use transformer in the system for the galvanic isolation purpose. However, usage of transformers makes the system bulky size and increase the cost of the system. The aforementioned problem makes the researchers to concentrate on transformerless PV system [7,8]. The growth of power electronics technology has made transformerless PV inverter well suited in kilowatt (kW) range by placing standards such as DIN VDE 01261-1. However, elimination of transformer creates leakage current [9, 10], and complication in the grid side controller. This paper gives the overview of recent advances in controllers in grid connected PV system. Section 2 illustrates standard codes and regulation of PV inverter followed by performance requirements in section 3. Control structure of PV inverter defined in detail with active power and direct power control method in section 4. Recent advances in single phase and three phase synchronization method is analysed in section 5.